Abstract

Our goal is to obtain a planar deposition of dense, thin and oriented carbon nanotubes membrane. We used the dielectrophoresis technique, where an electrical field orientates uncharged particles suspended in a liquid solution. Additionally, we will discuss the benefits of using self orientation of liquid crystals in addition to our method. Four different surfactants have been tested, two ionic surfactants, Sodium Dodecyl Sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS), and two anionic ...

Our goal is to obtain a planar deposition of dense, thin and oriented carbon nanotubes membrane. We used the dielectrophoresis technique, where an electrical field orientates uncharged particles suspended in a liquid solution. Additionally, we will discuss the benefits of using self orientation of liquid crystals in addition to our method. Four different surfactants have been tested, two ionic surfactants, Sodium Dodecyl Sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS), and two anionic surfactants, the Pluronics PE6400 and PE6800. Not only theirs capacities of dispersion were analyzed but theirs post-alignment elimination as well. These surfactants can also act as liquid crystal. This means that their structures changes with concentrations and temperature. Another dispersion, without any surfactant, using 1,2-dichlorobenzene as solvent, was also analyzed. To promote the alignment by dielectrophoresis, the electrical field was applied to these solutions, inside of the concentration range of dispersible capability, as a function of the variables which can affect the dielectrophoresis forces: frequency, magnitude and the AC/DC fields ratio. The tests showed that the alignment of carbon nanotubes is characterized by its agglomeration in a “rope” shape in the gap giving a good aligned structure. The SDBS has the best solubilization power; however, the SDS allows a better surfactant removal after aligment. The PE6800 can make a good dispersion but it was not enough to hold on through the centrifugation. Nevertheless the PE6400 doesn’t even make a visual good dispersion. The 1,2-dichlorobenzene solution shown a weak but stable capability of dispersion after the centrifugation, but terrible orientation power. Electric measurements were coherent with the images giving a qualitative way to estimate the carbon nanotubes orientation rate, but specially showing the efficiency of the surfactant removal process. ...

Institution

Universidade Federal do Rio Grande do Sul. Escola de Engenharia. Curso de Engenharia de Materiais.